Two-stroke diesel engines are well known and used excessively in various applications. The main application belongs to the transportation means like cars, bikes, locomotives, boats etc. Great advantages of two-stroke diesel engines are their simplicity, low coast and high power to weight ratio. During long and successful use of said engines numerous efficiency problems became apparent. It is common knowledge of those skilled in the art that said engines are less efficient than four-stroke engines of various types. It is believed that deficiencies are caused by incomplete air charge and incomplete exhaust. Four-stroke engines have separate dedicated pistons' movements for each of these functions.
Though attempts have been made to remedy the deficiencies, still to the best of our knowledge, two-stroke engines remain inferior to those four-stroke ones. The presented invention discloses a novel design of engines which significantly increases efficiency of two-stroke diesel engines. There are two principal goals of this invention that in turn allow for a number of further improvements and advantages. The first goal is to significantly increase the pressure of an air charge above the pressure of exhaust gases at the end of the expansion phase. This excessive pressure is instrumental for pushing-out of the exhaust gases, or, alternatively, for squeezing those exhaust gases into insignificant part of the combustion cylinder. In any case, having the air charge at a pressure multiple times higher than that of the exhaust gases will eliminate scavenging deficiency of the engine. The second goal of this invention is to lower the residual or return volume of the air charge to limit a choke effect. We define residual or return volume as a part of the air charge which is compressed and therefore heated, but does not make it into the combustion cylinder. At the following intake phase that return portion of the charge expends reaching the pressure of the intake air and consequently occupies large portion of the pumping cylinder. This repeatable effect reduces effective intake volume and partially chokes the engine. Our invention discloses the apparatus minimizing return volume and therefore greatly reducing said choke effect.
Important consequence of said two goals is a double compression cycle. Due to the pumping cylinder being necessarily many times larger than the combustion cylinder, the resulting total compression ratio for the air charge, by the moment of the fuel injection, will be the result of multiplication of the compression ratio of the combustion cylinder by the volume ratio of the pumping cylinder and the combustion cylinder. It is quite conceivable that said total compression ratio could be more than a hundred. There is a significant increase in thermal efficiency of the engine due to said outstanding compression ratio.